In a stage device which performs alignment, a drive reaction force generated when a stage is driven causes vibration or deformation to influence the alignment accuracy. This influence poses a problem, particularly in a field, e.g., a stage device used in an exposure apparatus, which requires high accuracy.
As a mechanism which cancels the drive reaction force of a stage, in Japanese Patent Laid-Open No. 111-243132, mass bodies are provided to a base, which supports the stage. Referring to FIG. 15, mass bodies (113a, 113b), which can be driven in an X direction, and mass bodies (113c, 113d), which can be driven in a Y direction, are provided to a base (109) which supports a stage (105) which moves in X and Y directions along guides (121, 107). A rotary mass body (not shown), which generates a rotational torque, is provided to the base. With this structure, the mass bodies are driven to cancel stage drive reaction forces in the X and Y directions and a θ direction (rotational direction about a Z-axis), so as to decrease the influence of the vibration caused by the drive reaction force.
In Japanese Patent Laid-Open No. 11-190786, a base that supports a stage is movable. Referring to FIG. 16, a base (109), which mounts a stage 105 thereon, is movably supported on a board (110) through an air bearing. Rotatable rotors 108 are arranged on the side surfaces of the base and in it. With this structure, the drive reaction force of the stage in the X and Y directions is canceled when the base moves, and the drive reaction forces in a θ direction, an ωx direction (a rotational direction about an X axis), and an ωy direction (a rotational direction about a Y axis) are canceled when the rotors rotate.
In recent years, the diameter of the wafer increases to increase the productivity of the devices, and the size of the stage also increases in proportion to the diameter of the wafer. Accordingly, the weight of the stage also increases. In order to increase the throughput (the number of wafers that can be processed within a unit time), the stage must be moved faster, and tends to be moved with a high acceleration. Namely, as the stage weight and stage acceleration increase, the thrust of the stage increases to be larger than before.
As in Japanese Patent Laid-Open No. 11-190786, in a structure in which the reaction force is canceled by moving the base in the X and Y directions with respect to the board, a space must be reserved for the moving stroke of the base. For this purpose, the size of the entire stage device increases, and consequently, the exposure apparatus itself becomes bulky.
The stroke of the base may be decreased by increasing the weight of the base. When transportation and maintenance of the stage device are taken into consideration, the weight of the base cannot be increased much.
In the case of levitating the base by an air bearing, when the base having a weight of several tons is to be levitated by the air bearing, the air bearing must have an accordingly large load capacity. When the load capacity of the air bearing is increased, however, the flow rate of air to be supplied must also be increased. Such a stage device is sometimes difficult to install, depending on the specifications of the utilities of the installation site.
As in Japanese Patent Laid-Open No. 11-243132, if the mass bodies are provided to the side surfaces of the base, the installation space increases undesirably. As the masses hang, they may undesirably deform the base or degrade the posture of the base.